1. Field of the Invention
The present invention relates to a support for a lithographic printing plate and a presensitized plate. More particularly, the present invention relates to a presensitized plate excellent in printing performance (for example, press life, scum resistance, sensitivity and cleaner press life or the like) when a lithographic printing plate is prepared and handling property (scratch resistance, fatigue fracture strength or the like), having very uniform and fine pits on the surface of the support and the support for a lithographic printing plate used for the same. Specifically, the present invention relates to the presensitized plate where development treatment can be performed with a developer substantially containing no alkali metal silicates after exposure, the support for a lithographic printing plate used for the same and the presensitized plate where dotted exposure defective areas called dot residual layers are unlikely to occur in plate making using a laser source and the support for a lithographic printing plate used for the same, in addition to the aforementioned characteristics by attaching Si atoms to the surface of the support for a lithographic printing plate.
2. Description of the Related Art
A photosensitive presensitized plate with an aluminum plate as a support is widely used for offset lithography.
The lithography using the photosensitive presensitized plate like this is a printing system utilizing a property that water and an oil do not essentially mix, an area which receives water and repels an oily ink (hereinafter this area is referred to as “a non-image area”) and an area, which repels water and receives oily ink (hereinafter this area is referred to as “an image area”) are formed on the printing plate surface of the lithographic printing plate (prepared from the aforementioned presensitized plate) used for the lithography.
For an aluminum support for a lithographic printing plate (hereinafter merely referred to as “a support for a lithographic printing plate”) used for the lithographic printing plate, since the support is used so as to allow its surface to function as the non-image area, the support requires various opposite characteristics such as ones that hydrophilicity and water retention property are excellent, and that further, the adhesion with the image recording layer provided thereon is excellent or the like.
Known as a method of preparing the presensitized plate is generally the method that after graining treatment and anodizing treatment are performed on the surface of a sheeted or coiled aluminum to obtain a support for a lithographic printing plate, a photosensitive solution is coated on the support and is dried to form an image recording layer, and the support provided an image recording layers is cut into a desired size if required. After an image is printed, development processing is performed on the presensitized plate to prepare a lithographic printing plate.
In the method, it is effective to perform electrochemical graining treatment in an acid solution (also referred to as “electrolytic graining treatment” according to the present invention) in order to improve adhesion between the image recording layer and the support, and it is also effective to perform a surface treatment and coat an undercoat solution after anodizing treatment is performed.
If graining treatment including electrolytic graining treatment is performed, fine asperities (pits) are produced on the surface of the support. It is conventionally considered that by equalizing and increasing the diameters and deeping the depth, the adhesion between the image recording layer and the support is strengthened in the image area, and the image recording layers are not exfoliated or the like even though a number of sheets are printed, and that water retention property is excellent in the non-image area, scum is hardly generated since a large amount of fountain solution can be held on the surface thereof and thus, a presensitized plate excellent in printing property can be obtained. For example, the method of improving the shape and uniformity of electrolytically grained pits from such a viewpoint is proposed in JP 2000-108534 A, JP 2000-37965 and JP 2000-37964 A.